The compound of formula (I), the hydrate thereof, the crystal of the compound of formula (I), and the crystal of the hydrate of the compound of formula (I) are novel compounds, and the processes for producing these compounds are therefore novel producing processes. A compound represented by formula (V):
(wherein R3 represents

and L2 represents a hydrogen atom or a protecting group for a hydroxyl group) and a compound represented by formula (VI):
(wherein R2 represents a hydrogen atom or a protecting group for a carboxyl group and R4 represents a hydrogen atom or a protecting group for a hydroxyl group), or salts thereof, which are important intermediates for the above-described compounds, are novel compounds, and processes for production the same are therefore novel producing processes.
A compound of formula (II) which is a precursor for the compound of formula (I) is a well-known compound, and known to be useful as an insulin sensitizing agent, a prophylactic or therapeutic agent against diabetes, a prophylactic or therapeutic agent against syndrome X, a prophylactic or therapeutic agent against diabetic complications, a prophylactic or therapeutic agent against hyperlipemia, a hypolipidemic agent, a prophylactic or therapeutic agent against obesity, an osteoporosis-treating agent, an anti-inflammatory agent, or a prophylactic or therapeutic agent against digestive system diseases (see, for example, Patent Reference 1).
[Patent Reference 1] WO02/100812
The compound of formula (II) corresponds to a compound described in Example 329 of WO02/100812, but the patent document does not directly disclose the compound of formula (I), which comprises two molecules of the compound of formula (II) and a calcium element, a hydrate thereof, a crystal of the compound of formula (I), and a crystal of the hydrate of the compound of formula (I).